I picked up a 79 240D about 4 years ago with a seized engine.
The girl I bought it from said it just stopped on the freeway, and failed to go in a forward direction.
It ran out of oil because she did not check it. Learned a valuable lesson for sure.
I picked it up for $300. Shows 167K on the spedo, but we know how accurate the spedo`s are.
I pulled the head a couple weeks ago and sent it to a shop in Dallas, Tx. for a customer.
When I got it off the cam shaft looked good, turned smoothly, no scoring on the lobes etc...
Timing chain looked ok.
No cracks that I could see on the Head
I could not turn the engine before I removed the head, or after it was removed.
I soaked the cylinders with WD-40...all I had, and was out of Kroil
Just got in 2 cans of it and will soak it with the kroil to see what happens.
My guess is the Rod bearings are welded to the Crank.
I agree with leathermang, drop in your good engine, and in your spare time, take the sick one apart.